Figure 37, Wire rs-485 bus, Table 7 – Vaisala HMT330 User Manual
Page 62: Wire (switch 3: on)
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1102-028
Figure 37
4-Wire RS-485 Bus
Table 7
4-Wire (Switch 3: On)
RS-485 master
Data
HMT330
Tx D1+
→
Rx D1+
Tx D0-
→
Rx D0-
Rx D1+
←
Tx D1+
Rx D0-
←
Tx D0-
Stub
Termination
Termination
Termination
Termination
Twisted pair
120R
120R
120R
120R
Twisted pair
Stub
Stub
Baud > 19.2K Stub < 10ft, 3m
Baud > 112K Stub < 1ft, 0.3m
Rx D0-
Rx D1+
Common
Tx D0-
Tx D1+
Switch
Term off
Term off
2/4 wire on
RS422 off
Tx D0-
Tx D1+
Common
Rx D0-
Rx D1+
Switch
Term off
Term off
2/4 wire on
RS422 off
Tx D0-
Tx D1+
Common
Rx D0-
Rx D1+
RS485-1
RS485-1
Address MM
Address NN
RS485 bus master
Junction
box
Junction
box
Junction
box
Common
line
Common
line